Dark Motives and Elective Use of Brainteaser Interview Questions • Hacker News Board

Re: Dark Motives and Elective Use of Brainteaser Interview Questions

#181

Post by jfasi » Tue, Sep 11, 2018, 8:50 PM UTC

munchbunny wrote: post #175

jfasi wrote: post #7

As someone who does both a lot of interviewing (at Google) and gives a lot of advice on interviewing to people just starting out, this rhymes with my intuition about why some people get into interviews: even without the use of brainteasers (which, for the record, are not used at Google), the interview process is hard . People rarely come out of it without at least a twinge of frustration of humiliation. I'm not immun…

At risk of proposing a generalization, I think that this comes from the same place that other gatekeeping behaviors come from: you see yourself as the in-group's bouncer. That puts you in a mindset to run the interviewee through a gauntlet, partly as a ritual to show their desire to get in, and partly through a sense of duty to hire "only the best". But hiring is not a filtering problem. It's a matching problem. And…

I've been mentally drafting a blog post on exactly this topic, so while that percolates in my mind I'll answer with: it totally is a filtering problem.

For a small company whose culture is in flux and needs the right person, it's absolutely a matching problem. You need to find the right person for the job, period.

At the scale of a company like Google, however, it's absolutely a filtering problem. First off, we're large enough that most (perhaps not all) people talented enough to clear our interviews will (given enough persistence) find a place where they can be happy and contribute. We can get away with not worrying about the subtleties of matching and instead only focus on technical skills.

Second off, the number of applications rejected for every hire is staggering, simply because of how many people apply. These numbers are fantasy, but imagine if you had to choose one person out of a hundred applicants, and you actually had the means to interview every single one. You're going to pay this person a quarter of a million dollars a year and aim to keep them for half a decade or more. The economically rational thing to do is be picky as all hell, and this is exactly how Google and friends do it.

Re: Dark Motives and Elective Use of Brainteaser Interview Questions

#182

Post by PinkMilkshake » Tue, Sep 11, 2018, 8:53 PM UTC

8_hours_ago wrote: post #123

I recently interviewed at Apple and one interviewer caused me to decide to never work there. I was put into a conference room and had 8 people over 6 hours come in and interview me one after another. Each person asked me about my background and then jumped into a whiteboard coding problem. Most of the interviewers were understanding of the fact that writing code on a whiteboard is nothing like writing code on a compu…

> Don't they have calculators at Apple? Or phones, perhaps?

He must have been from the iPad dev team.

Re: Dark Motives and Elective Use of Brainteaser Interview Questions

#183

Post by pmiller2 » Tue, Sep 11, 2018, 8:56 PM UTC

01100011 wrote: post #143

8_hours_ago wrote: post #123

I recently interviewed at Apple and one interviewer caused me to decide to never work there. I was put into a conference room and had 8 people over 6 hours come in and interview me one after another. Each person asked me about my background and then jumped into a whiteboard coding problem. Most of the interviewers were understanding of the fact that writing code on a whiteboard is nothing like writing code on a compu…

I'm nitpicking, but yes sometimes you do have to code under pressure. Yes it can result in bad code but it can also save millions of dollars as production lines are allowed to run, ecommerce is allowed to happen, or important contractual obligations are met. That said, you generally do not write that code on a whiteboard with no access to the internet. It sounds like you just interviewed with a dick. That happens.

I don't believe your nitpick is valid here. True, sometimes one has to code under pressure, in the sense that money is lost (or, at least not made) while things are down, but there's almost never a situation where you can't stop and take an extra 20 or 30 minutes to check to see that your code would do what you expect it to do. In fact, if the worst consequence of waiting 30 minutes to deploy a temporary fix is that some more money gets lost, I would argue you should almost always do that rather than deploying code that might have even worse consequences.

Re: Dark Motives and Elective Use of Brainteaser Interview Questions

#184

Post by jarsin » Tue, Sep 11, 2018, 8:58 PM UTC

8_hours_ago wrote: post #123

I recently interviewed at Apple and one interviewer caused me to decide to never work there. I was put into a conference room and had 8 people over 6 hours come in and interview me one after another. Each person asked me about my background and then jumped into a whiteboard coding problem. Most of the interviewers were understanding of the fact that writing code on a whiteboard is nothing like writing code on a compu…

Next time just tell him you are a Millennial and you never heard of long division before.

Re: Dark Motives and Elective Use of Brainteaser Interview Questions

#185

Post by eip » Tue, Sep 11, 2018, 8:58 PM UTC

rrggrr wrote: post #47

eip wrote: post #44

Earlier quoted context omitted.

If you think anyone 'really' wants to build your shitty CRUD app then you are deluding yourself. Do you 'really' love your job? Would you do it for free?

Ouch. So, I'm not in the software business, but either way the point of my Q&A is measure the distance between what an employee wants to during the day versus what probably needs to be done to accomplish the desired result. When the gap is big the hire/job never works out.

> what an employee wants

What I 'want' to do during the day is be a sunscreen boy for the Reef bikini team.

What I am willing to tolerate in exchange for money is considerably wider ranging.

No one 'wants' to be trapped in some corporate soul sucking nightmare for five days a week.

Re: Dark Motives and Elective Use of Brainteaser Interview Questions

#186

Post by adrianmonk » Tue, Sep 11, 2018, 9:01 PM UTC

pinewurst wrote: post #9

jfasi wrote: post #7

As someone who does both a lot of interviewing (at Google) and gives a lot of advice on interviewing to people just starting out, this rhymes with my intuition about why some people get into interviews: even without the use of brainteasers (which, for the record, are not used at Google), the interview process is hard . People rarely come out of it without at least a twinge of frustration of humiliation. I'm not immun…

It's like military academy (or fraternity) hazing. You've been abused, therefore you want to pass the load of that abuse on. Maybe you delude yourself into calling it "tradition" or "high standards" or maybe you're just honest and enjoy the sadism of it all.

I have a pet theory that it's related to the difficulty of accepting a painful truth.

In that moment, you face a choice. Either you do the same thing that was done to you, or you don't.

If you break with tradition and avoid doing whatever it is, you will end up asking yourself why, and you'll have to answer "because it was abusive". It some cases, that thought may be too horrible to even admit into your mind, or at least it's unpleasant enough that you prefer not to deal with it.

If you go the other way and stick with tradition, then you can just do whatever it is, and you can say this happened to me, it's normal, it's part of the natural cycle of things, etc.

Also, sometimes you are blindsided by this and don't realize you're making the choice until the moment it happens, so you don't have time to mentally prepare to do the harder thing.

Point being, it's not always sadism. Sometimes it's denial.

TLDR: The corollary of "that would be abusive" is "I've been abused". It hurts to confront that possibility, so people look for ways to deny it. And the organization offers them one.

Re: Dark Motives and Elective Use of Brainteaser Interview Questions

#187

Post by gamegoblin » Tue, Sep 11, 2018, 9:01 PM UTC

pzh wrote: post #118

illumin8 wrote: post #77

Earlier quoted context omitted.

I interviewed at Google (back in 2005, mind you) and I remember being asked a couple brain teaser questions like how to estimate the number of windows in NYC. I will say that out of my loop, there were only 2 interviewers that came across as intentionally mean, the rest were genuinely wanting to see how I solved problems and understand what my thought process was, which is what most interviewers should be attempting…

Aren't the examples of brainteasers actually Fermi problems? Maybe they sound like brainteasers if asked without the appropriate context, but when you're doing a system design interview and you have to estimate your throughput or storage requirements, you're effectively solving a Fermi problem just like the one that asks you to estimate the number of windows in NYC.

Most of the "estimate foo" problems are Fermi problems. E.g. The classic one I've heard is "estimate the number of piano tuners in the world". The route I took to do so is:

      number of people in the world
    / average number people per piano
    * average number of times a piano is tuned per year
    * average amount of hours to tune a piano
    / average number of hours a piano tuner works per day
    / average number of days a piano tuner works per year

So in terms of units, the flow is:

       people
    -> pianos
    -> piano tunings per year
    -> hours spent tuning pianos per year
    -> workdays spent tuning pianos per year
    -> piano tuners

This is all very similar to dimensional analysis most people will learn in a highschool science class.

Just to plug in some random numbers, let's pick 7 billion people, 100 people per piano, 0.3 tunings per year, 1 hour to tune a piano, 3 hours of tuning per day and 100 days per year(I imagine it's part-time for most piano tuners...). We arrive at:

    7,000,000,000 / 100 * 0.3 * 1 / 3 / 100 == 70,000

And, for what it's worth, at least in my field, we do these sorts of ballpark estimations all the time to determine feasibility of systems.

I've never had one of these in an interview setting, but I imagine the important thing is to demonstrate the line of reasoning rather than actually arriving at a concrete number.

Re: Dark Motives and Elective Use of Brainteaser Interview Questions

#188

Post by traek » Tue, Sep 11, 2018, 9:02 PM UTC

nicoburns wrote: post #131

hectormalot wrote: post #121

Earlier quoted context omitted.

“I’d like to understand how you structure problems, we can do a different topic if you like?” “With ~50M people capable of clicking ads, and assuming they click one ad a day at 20cnt CPC, it would be around 3.6bn. I think my assumptions are on the high side, but order of magnitude is probably correct” If done well, solving a problem (not a brain teaser) together can yield insight in how people approach new challenges…

What I find weird about these questions, is that they are expected to be answered without any research? How often do you expect your people to solve a problem in a domain they know nothing about without doing any research? And the given example is odd, a lot of useful information that would help to answer the question will be public, and the obvious way to answer the question would be to look it up, before estimating…

It's about knowing how to structure problems, whether the components are public or whether the problem space is completely unfamiliar.

E.g. someone who guesses "$3 billion" on only a gut feeling likely wouldn't be a strong hire even if the number is correct, while someone who can correctly decompose the final answer into its components and make reasonable estimates would be a much better candidate.

For estimation interview questions, and problem-solving questions more generally, a "structural" approach to breaking down problems is important because on the job the interviewee will need to be able to identify what levers are available to them.

Re: Dark Motives and Elective Use of Brainteaser Interview Questions

#189

Post by pmiller2 » Tue, Sep 11, 2018, 9:12 PM UTC

spitfire wrote: post #105

Hunter and Schmidt did a meta-study of 85 (now 100, with the follow up) years of research on hiring criteria. [1] There are three attributes you need to select for to identify performing employees in intellectual fields. - General mental ability (Are they generally smart) Use WAIS or if there are artifacts of GMA(Complex work they've done themselves) available use them as proxies. Using IQ is effectively illegal[2] i…

What sort of meaningful work sample test can you do in 3 hours?

Re: Dark Motives and Elective Use of Brainteaser Interview Questions

#190

Post by pmiller2 » Tue, Sep 11, 2018, 9:15 PM UTC

RodgerTheGreat wrote: post #144

framebit wrote: post #69

I had one of these brainteaser questions in an interview once, and I liked my mathematician friend’s answer to it the best. Q: Given infinite setup time and infinite money, how would you fill the inside of a 747 with ping pong balls as quickly as possible? A: Define the inside of the plane as the exterior. Now, by definition, all ping pong balls are inside the plane. QED.

All ping pong balls may now be "inside" the plane, given this approach, but he's done a horrendously poor job of filling the plane.

Not really. It is as full as possible. :)